Low temperature flux creep in high- Tc superconductors

An exact solution describing flux creep in high-T{sub c} superconductors at low temperatures was found, assuming the creep activation barrier U grows logarithmically with decreasing current j: U = U{sub 0} ln(j{sub 0}/j). The magnetic relaxation of single crystal Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8} was measured at moderate temperatures and magnetic fields. Two different regimes corresponding to the partial and full penetration of the magnetic field into the sample were found. The observed magnetic relaxation behavior is in a good agreement with the model proposed. 19 refs., 4 figs.